On demand radiation induced constructive and deconstructive chemical reactions

ABSTRACT

A method is provided for decomposition of a polymeric article, wherein the polymeric article contains a polymer and one or more energy modulation agents, by applying an applied energy to the polymeric article, wherein the one or more energy modulation agents convert the applied energy into an emitted energy sufficient to cause bond destruction within the polymer.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No.15/590,181, filed May 9, 2017, now allowed, which is a Continuation ofU.S. application Ser. No. 15/183,110, filed Jun. 15, 2016, now U.S. Pat.No. 9,676,918, and also claims priority to U.S. Provisional applicationSer. No. 62/175,683, filed Jun. 15, 2015, the entire contents of each ofwhich are hereby incorporated by reference. The present application isrelated to U.S. Provisional application Ser. No. 62/018,915, filed Jun.30, 2014, entitled IMPROVED ADHESIVE BONDING COMPOSITION AND METHOD OFUSE, the entire contents of which are hereby incorporated by reference.The present application is also related to PCT applicationPCT/US2015/021307, filed Mar. 18, 2015, entitled IMPROVED ADHESIVEBONDING COMPOSITION AND METHOD OF USE, the entire contents of which arehereby incorporated by reference. The present application is alsorelated to U.S. Provisional application Ser. No. 61/955,547, filed Mar.19, 2014, entitled ADHESIVE BONDING COMPOSITION AND METHOD OF USE, theentire contents of which are hereby incorporated by reference. Thepresent application is related to U.S. Provisional application Ser. No.61/955,131, filed Mar. 18, 2014, entitled ADHESIVE BONDING COMPOSITIONAND METHOD OF USE, the entire contents of which are hereby incorporatedby reference. The present application is related to U.S. Provisionalapplication Ser. No. 61/331,990, filed May 6, 2010, and U.S. Provisionalapplication Ser. No. 61/443,019, filed Feb. 15, 2011, the entirecontents of each of which are hereby incorporated by reference. Thepresent application is also related to U.S. provisional patentapplication 61/161,328, filed Mar. 18, 2009; U.S. provisional patentapplication 61/259,940, filed Nov. 10, 2009; U.S. ProvisionalApplication Ser. No. 60/954,263, filed Aug. 6, 2007, and 61/030,437,filed Feb. 21, 2008; U.S. application Ser. No. 12/059,484, filed Mar.31, 2008; U.S. application Ser. No. 11/935,655, filed Nov. 6, 2007; U.S.Provisional Application Ser. No. 61/042,561, filed Apr. 4, 2008;61/035,559, filed Mar. 11, 2008; and 61/080,140, filed Jul. 11, 2008;U.S. patent application Ser. No. 12/401,478 filed Mar. 10, 2009; U.S.patent application Ser. No. 11/935,655, filed Nov. 6, 2007; U.S. patentapplication Ser. No. 12/059,484, filed Mar. 31, 2008; U.S. patentapplication Ser. No. 12/389,946, filed Feb. 20, 2009; and U.S. patentapplication Ser. No. 12/417,779, filed Apr. 3, 2009, the entire contentsof each of which is hereby incorporated by reference. This applicationis related to U.S. patent application Ser. No. 13/102,277 filed May 6,2011, the entire contents of which is hereby incorporated by reference.This application is related to U.S. patent application 61/735,754 filedDec. 11, 2012, the entire contents of which are hereby incorporated byreference.

FIELD OF INVENTION

The invention pertains to the activation of suitably reactivechemistries inside polymeric materials to induce constructive chemicalreactions such as curing; and, subsequently, having the ability toinduce on demand the degradation of such polymeric materials. Suchpolymeric degradation facilitates the recycling of bonded parts andhighly cross-linked polymer networks such as rubber tires. Suchconstructive and deconstructive chemical reactions are induced by thecombination of an initiating radiation having suitable photonic energyand depth of penetration along with chemical additives that modulate theinitiation energy.

DISCUSSION OF THE BACKGROUND (Photo-Degradation, Chain Scission inBiological Polymers):

Polymers are used in a wide range of applications from compositestructures, automobile tires and adhesives to athletic shoes and fibersand are well known. One particularly important application subsequent toall domains of manufacturing is the field of reclaiming and recyclingfrom already manufactured parts that have reached their end of life.Adhesives have proliferated many assembling processes to bond dissimilarparts. The properties of the bonding adhesive can be tailored to thepart. Commercially available materials are formulated to meet variousrequirements, and in addition to the monomer(s) may contain particulatefillers such as metal, oxides, or dielectric powders, as well as variousadditives to control thermal conductivity, viscosity and otherproperties. However, once the functional life of a given product is overit becomes desirable to be able to reclaim valuable parts of the product(such precious metals) and recycle subassembly from the products (suchas plastics) that can be reground for re-melting and re-use in makingnew products. The economics of recycling are not trivial. The more time,energy, and effort are involved to enable recycling, the lesseconomically viable it becomes to harvest from old products to make newones. The easier the methods that can be used to disassemble to reclaimand recycle, the better it is from a manufacturing stand point. Also,minimizing contamination of recycled products and recovering rawmaterials with the least contamination, the better it is from aneconomic stand point. For these reasons, methods that enable thedisassembly of bonded parts (in pristine forms) would be highlydesirable. A set of related technologies encompassing process, apparatusand methods are provided herein to take an existing polymer network thatis highly reacted with good properties through an efficient degradationprocess to depolymerize it for ease of removal and de-bonding of jointparts while maximizing yield.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide reactivechemistries and associated methods of use to enable two objects tobecome de-bonded across their interface under X-Ray, e-beam and UVradiation that can be cured by chain scission, minimization of crosslinks, a combination of chain scission and breakage of crosslinks in theabsence of line-of-sight. The novel reactive chemistries across aninterface between two objects have to be complimentary and compatiblewith the reactive chemistries needed to form the adhesive leading tobonding as a first step of the process.

A further object of the present invention is to provide a method forde-bonding objects contained in an article at an interface between theobjects, wherein the objects are joined at the interface through anintermediate layer by causing destruction of bonds within theintermediate layer through an applied energy.

Another object of the present invention is to provide a method for thedecomposition of a polymeric article which contains one or more energymodulation agents by applying an applied energy to the polymericarticle, wherein the one or more energy modulation agents convert theapplied energy into an emitted energy sufficient to cause bonddestruction within the polymer.

These and other objects of the present invention, individually or incombinations thereof, have been satisfied by the discover of a methodfor de-bonding objects contained in an article at an interface betweenthe objects, wherein the objects are joined at the interface through anintermediate layer, comprising:

applying energy from a radiation source, wherein the energy issufficient to cause destruction of bonds within the intermediate layer;and

separating the two objects from one another.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 shows a graphical representation of an embodiment of an adhesiveassembly used according to the present invention.

FIG. 2 shows a graphical representation of an embodiment of an adhesiveassembly used according to the present invention.

FIG. 3 shows a graphical representation of an embodiment of an adhesiveassembly used according to the present invention.

FIG. 4 shows a graphical representation of another embodiment of thepresent invention using an adhesive assembly.

FIG. 5 shows a graphical representation of a further embodiment of thepresent invention using an adhesive assembly having a primed surface onone of the substrate portions.

FIG. 6 shows a graphical representation further embodiment of thepresent invention using an adhesive assembly having a primed surface onboth of the substrate portions.

FIG. 7 shows a graphical representation of irradiating an adhesiveassembly depicted in FIG. 5 with X-rays while submerged in an acid washbath to speed decomposition.

FIGS. 8A-8E are graphical representations of various forms ofsuperposition of multiple plies in a multi-ply composite construction.

FIG. 9 is a graphical representation of the use of primer layers betweenadjacent plies in a multi-ply composite construction, from which thepresent invention can deconstruct the multi-ply structure and recoverseparate ply layers.

FIG. 10 is a graphical representation showing the use of an embodimentof the present invention to deconstruct vulcanization bonds present inrubber compositions.

FIGS. 11A-11E are graphical representations showing various types ofcoated and uncoated phosphors according to the present invention.

FIGS. 12A-12B are graphical representations showing coated mixedphosphor aggregates according to the present invention.

FIGS. 13A-13D are graphical representations showing the preparation ofconformable phosphor coated films using a draw knife, cutting the filmsinto desired die-cut shapes, and the ability of these films toaccommodate stretching and maintaining its form across complexinterfaces.

FIG. 14 is a schematic depicting conversion of primary and scatteredinitiating energy such as x-rays by energy modulation agents in amedium.

FIG. 15 is a schematic depicting x-ray scattering events andinteractions with energy modulation agents in the medium

DETAILED DISCUSSION OF THE PREFERRED EMBODIMENTS

An aspect of the present invention pertains to process, chemistries,applications and methods related to the incorporation of specialchemistries (special additives) to be embedded in polymeric materials(including organic, inorganic and biological polymers), whereby theresultant formulation can be processed by first imparting energy(including but not limited to UV light, heat, X-Ray, E-beam) to promotechemical reactions (including but not limited to the formation ofadduct, cross-linkages, addition); and, subsequently, after an elapsedtime ranging from months to years depending on the intended functionallife, the polymeric material can be made to undergo deconstructivereaction(s) to degrade (though loss of structural integrity, downsizingof molecular weight, breakage of crosslinks, breakage of specific bondsto name a few examples). The deconstructive chemical reactions arecaused by exposing the polymeric material to a deeply penetratingradiation capable of being modulated by the special additives that inturn emit a least one radiation (distinct for the initiation radiation)which is capable of effectively causing the degradation of the saidpolymer(s) that have undergone an initial constructive reaction.

In one case of the present invention, the attributes of the novelmaterial chemistry include, but are not limited to, the ability to formfree radicals and to cause bond scission under X-Ray energy. Theaddition of UV radiation to X-Ray radiation leads to enhanced freeradical formation and bond scission. The addition of heat to the UV andX-Ray energies leads to further enhancement of the free radicalformation and bond scission leading to deconstructive reactions in thepolymer network.

There are various possibilities for depolymerizing a network includingthe use of a highly energetic light such as UV light. Typically,depolymerization needs a direct exposure to UV light to occur where onesurface is permeable to direct UV exposure enabling depth of penetrationof such highly catalytic light. Most adhesives do not allow UV topenetrate more than a few atomic layers up to possibly microns, whichmake the application of external light ineffective at depolymerizing anestablished polymer network. However, with the use of special additives(preferably in powder form like phosphors) possessing the ability tomodulate a highly energetic incident radiation with depth of penetrationcapability, such as X-Ray or E-beam, into UV light, a technology pathwayto have dispersed UV centers across a polymer network can be utilizedfor depolymerizing purposes. This phosphor mediated technology canenable mechanisms within the thickness of adhesives that are enclosedwith no line of sight and the materials need not to be UV transparent.Such degradation mechanisms include: 1-Photo-degradation of polymerbackbones via exposure to UV radiation (in UVA, UVB and UVC) and2-Cleavage of molecular backbones via exposure to UV radiation. Extendedexposure to ultraviolet (UV) radiation may cause the significantdegradation of many materials.

UV radiation causes photo oxidative degradation which results inbreaking of the polymer chains, produces free radical and reduces themolecular weight, causing deterioration of mechanical properties andleading to useless materials after an unpredictable time. For example,Polystyrene (PS), one of the most important material in the modernplastic industry, has been used all over the world due to its excellentphysical properties and low-cost. When polystyrene is subjected toextended levels of UV radiation especially in the presence of air, itundergoes a rapid yellowing and a gradual embrittlement. The mechanismof PS photolysis in the solid state (film) depends on the mobility offree radicals in the polymer matrix and their bimolecular recombination.Free hydrogen radicals diffuse very easily through the polymer matrixand combine in pairs or abstract hydrogen atoms from polymer molecules.Phenyl radicals have limited mobility. They may abstract hydrogen fromthe near surrounding or combine with a polymer radical or with hydrogenradicals.

The use of plastics in building applications is popular in thedeveloping world because of the low cost and the ease of use of plasticcomponents compared to the conventional metal, glass, mortar, wood andother materials. Plastics are used in other products such as outdoorfurniture, fishing gear, and marine craft, which are also routinely usedoutdoors. Solar radiation reaching the surface of the earth ischaracterized by wave lengths from approximately 295 up to 2500 nm. Thesolar radiation classified as UV-B (280-315 nm) has an energy of 426−380KJ mol−1. Fortunately, the higher energetic part of UV-B; 280-295 nm, isfiltered by the stratosphere and does not reach the earth's surface,UV-A (315-400 nm), has energy between 389 and 300 KJ mol−1 and is lessharmful for organic materials than UV-B. Visible (400-760 nm). If thephoto induced degradation is initiated on the inside of the polymer,then all wavelengths can be utilized to influence rapid degradation.

Photodegradation is degradation of a photodegradable molecule caused bythe absorption of photons, particularly those wavelengths found insunlight, such as infrared radiation, visible light, and ultravioletlight. However, other forms of electromagnetic radiation can causephotodegradation. Photo degradation includes photo dissociation, thebreakup of molecules into smaller pieces by photons. It also includesthe change of a molecule's shape to make it irreversibly altered, suchas the denaturing of proteins, and the addition of other atoms ormolecules. A common photo degradation reaction is oxidation. Photodegradation in the environment is part of the process by which ambergrisevolves from its fatty precursor. Light-induced polymer degradation,or photo degradation, includes the physical and chemical changes causedby irradiation of polymers with ultraviolet or visible light. In orderto be effective, light must be absorbed by the substrate (polymericsystem). Thus, the existence of chromophoric groups in themacromolecules is a pre-requisite for the initiation of anyphotochemical reaction.

Ketones, quinines, and peroxides are initiators for different reactiondegradation or chemical modification occurring in organic compounds.They absorb light up to about 380 nm, which causes their excitation orcleavage to radicals. One may initiate polymer degradation and othertransformation by abstraction of hydrogen atom from a macromolecule (PH)and formation of polymer alkyl radical (P.) The influence oflow-molecular weight organic compounds such as benzophenone (BPh),anthraquinone (AQ) and benzoyl peroxide (BPo) on the photo processes ofpolystyrene has been studied. The results indicate that additivesaccelerate and increase the photo degradation and photo oxidation ofpolystyrene. Photo degradation may occur in the absence of oxygen (chainbreaking or cross-linking) and the presence of oxygen (photo oxidative)degradation. The photo oxidative degradation process is induced by UVradiation and other catalysts (or both) and can be accelerated atelevated temperatures. Photo degradation of polystyrene (e.g.embrittlement and color change) can take place upon irradiation with aportion of UV light that is contained within sun light.

Nickel chelates are very effective quenchers of the triplet state ofcarbonyl groups in polyolefins. These chelates have been tested forphotostabilization of polyisobutylene, poly butadiene Lala and Rabek(1980), polystyrene George (1974), PVC, poly(2,6-dimethyl-1,4-phenyloxide) and poly urethanes. (Chandra 1983; Osawaet al. 1979).

Nickel chelates can photostabilize a polymer by one or more of thefollowing mechanisms.

-   -   (i) Quenching of the excited state of carbonyl groups (ketones)        through energy transfer.    -   (ii) Quenching of the singlet oxygen (102)    -   (iii) Decomposition of the hydroperoxides (OOH) radical, to non        radical inactive species        These compounds operate by reacting directly with polymeric        hydroperoxide (ROOH). The decomposition of hydroperoxide in        polymer to non radical derivatives was first demonstrated by        Carlsson and Wiles (1974). Many metal complexes of sulphur        containing ligands such as dialkylthiocarbonate and        dialkylthiophosphate not only decompose hydroxide in PE film but        are also effective in UV stabilization (as UV absorbers and        excited state quencher).

Almost all synthetic polymers require stabilization against adverseenvironmental effects. It is necessary to find a means to reduce orprevent damage induced by environmental components such as heat, lightor oxygen. Research into degradation and ageing of polymers is extremelyintensive and new materials are being synthesized with a pre-programmedlifetime. There are many possible ways of polymer degradation:thermolysis, thermos oxidation, photolysis, photo oxidation, radiolysisetc. With the goal to increase lifetime of a particular polymericmaterial, two aspects of degradation are of particular importance:Storage conditions, and Addition of appropriate stabilizers. A profoundknowledge of degradation mechanisms is needed to achieve the goal.

The term degradation of macromolecules denotes all processes which leadto a decline of polymer properties. It may eventually involve physicalprocesses, such as polymer recrystallization, or denaturation of proteinstructures. Chemical processes related to degradation may lead to areduction of average molar mass due to macromolecular chain bondscission or to an increase of molar mass due to crosslinking renderingthe polymer insoluble. A wide variety of synthetic and naturallyoccurring high polymers absorb solar ultraviolet radiation and undergophotolytic, photo-oxidative, and thermos-oxidative reactions that resultin the degradation of the material.

In recent years, the use of polymeric materials has rapidly increasedbut it is well established that rapid photo-degradation of thesematerials is possible when they are exposed to natural weathering(Guillet 1985; Hamid 2000; Rabek 1996; Bottino et al. 2003). This is aserious issue, with economic and environmental implications andtherefore a large effort is focused on under-standing the changes thatoccur at molecular level and the degradation kinetics. Followingdifferent routes, UV radiation causes a photo-oxidative degradationwhich results in breaking of the polymer chains, produces radical andreduces the molecular weight, causing deterioration of mechanicalproperties and leading to useless materials, after an unpredictable time(Bottino et al. 2003; Gardella 1988). Damage by UV radiation is commonlythe main reason for the discoloration of dyes and pigments, weathering,yellowing of plastics, loss of gloss and mechanical properties(cracking), sun burnt skin, skin cancer, and other problems associatedwith UV light. Most of the common polymers used in such applicationscontain photo stabilizers to reduce photo damage and to ensureacceptable life times under outdoor exposure conditions; without theseadditives, the UV induced degradation may proceed unchecked.

Biological Polymers Cleavage

A light-activated reagent that can bind to protein molecules and thensever them when irradiated by a 344-nm light could offer microbiologistsa versatile tool for exploring the structure and behavior of proteins.Scientists could use this tool to sequence and manipulate proteins,controlling the reagent's scissor-like effect precisely, in part becausethe reagent can be selectively activated and in part because themolecule will bind only in specific sites on the protein.

The reagent was designed and studied by researchers at the University ofConnecticut in collaboration with Glaxo Wellcome in Research Triangle,N.C., and Columbia University in New York. “So far we looked at severalwavelengths from 310 to 380 nm, and the cleavage efficiency varies. Themolecule absorbs light very strongly at [the 344 nm] wavelength,” saidChalla V. Kumar, an associate professor of chemistry at the Universityof Connecticut.

The designer molecule, N-(phenylalanine)-4-(1-pyrene)butyramide, orPy-Phe, binds in specific sites. The pyrene part is hydrophobic, and thephenylalanine carboxyl part is hydrophilic, so Py-Phe will bind on aprotein only where a hydrophobic site is adjacent to a hydrophilic one.

Genetic Applications

Chemists and biologists speculate that the molecule can be used as ageneral reagent for cutting proteins, which would make it useful formolecular studies of proteins and peptides. Researchers have shown thata Py-Phe molecule can bind to lysozyme and albumin proteins and splitthem cleanly in two. “Many techniques can cut a protein with enzymesthermally,” said Miguel Garcia Garibay, associate professor of chemistryat UCLA. But such methods make no distinction between events, so aresuitable only for studying material in steady state. “This technique canbe activated precisely, so it has applications in genetics to studyprocesses of [molecular] interaction within a defined time span,”Garibay said.

Kumar expects to begin tests on streptavidin, cholesterol oxidase andother key proteins involved in human disease states. “If we canselectively photodestruct key proteins, then we may target cancer cellsor specific pathogens,” he said.

To activate the protein scissors, researchers used a lamp and amonochromator. Light raises the Py-Phe radical to an excited state,initiating a sequence of molecular reactions that split the peptidebond.

Various examples of such polymeric materials intended in the presentinvention are provided by way of illustration and not a full inclusionof the scope of the present invention. These examples include adhesives,primers, poly-dAdT, DNA and cross-linked rubbers to name a few.

Adhesives (Groups 1, 2, 3 & 4):

An aspect of the present invention pertains to special additives to beembedded in standard or specialty adhesives, whereby the resultantformulation can be cured using standard curing methods (including UVlight, heat, X-Ray, E-beam and part A: part B reactive chemistries ofthe appropriate stoichiometry); and, subsequently, the cured adhesivecan be broken from within the adhesive thickness by applying a specialenergy with deeply penetrating property (such as X-Ray and E-beam), thatcan interact with the special adhesive and causes the structuraldisintegration of the special adhesive via different pathways includingbut not limited (the deterioration of the polymeric chains, theinducement of shorter molecular weights, the scission of certainmolecular bonds, the reduction of crosslink density or the breakage ofthe cross-linkages). As such, the special adhesive according to theembodiments of the present invention comes apart and the assemblies (orsubassemblies) that were bonded can be separated. The recovery of theassemblies and subassemblies can be done with higher yield compared toother methods hence facilitating any subsequent recycling steps. Atleast one part needs to have the special adhesive for bonding 2different assemblies or subassemblies.

Certain embodiments of the present invention can preferably be practicedby using standard (commercially available) adhesives or by usingspecialty adhesives as outlined in the four following groups:

Group 1:

Commercially available polymeric adhesives, including, but not limitedto, 2 part adhesives, UV curable adhesives and thermally curableadhesives, can be used in accordance to the current invention by addinga special additive (preferably in powder form). The additive can beadded by weight percent in the range of 1% to 30%. The Commerciallyavailable adhesive is then cured using the recommended curing methods.The 2 parts assembly (or subassemblies) that have been joined using thecommercially available adhesive goes through its functional life (thatcan be 5 years for an inkjet housing). After the functional life is overand the part is needed to be recycled then the assembly or subassemblyis exposed to X-Ray where the special additives embedded in the adhesiveabsorb X-Ray energy and emits UV energy suitable for breaking bonds ofthe curable adhesive to make dis-assembling process easier and ondemand. The various de-bonded parts (de-bonded assemblies orsubassemblies) can be recycled. FIG. 1 shows a graphical depiction ofthis type of assembly wherein Parts A (10) and B (20) are joined usingcommercially available adhesive containing the special additive able tomodulate deeply penetrating radiation (31).

Group 2:

Commercially available polymeric adhesives (of various kinds) including2 part adhesives, UV curable adhesives and thermally curable adhesivescan be used in accordance with the present invention by modifyingcertain bonds within the polymeric adhesive and chain and by adding aspecial additive (preferably an energy modulation agent, and preferablyin powder form). The additive can be added by weight or mole percent inthe range of 1% to 30%. The Commercially available adhesive is thencured using the recommended curing method. The 2 parts assembly (orsubassemblies) that have been joined using the commercially availableadhesive goes through its functional life. After the functional life isover and the part is needed to be recycled then the assembly orsubassembly is exposed to X-Ray where the special additive absorbs X-Rayenergy and emits UV energy suitable for breaking bonds of the curableadhesive to make the dis-assembling process easier and on demand. FIG. 2shows a graphical depiction of this type of assembly wherein Parts A(10) and B (20) are joined using commercially available adhesive thatinclude the modification of certain bonds and that contain specialadditives able to modulate deeply penetrating radiation for structuraldisintegration of the adhesive (32).

Group 3:

UV curable polymeric adhesives (of various kinds) that can be curedusing a first initiating energy that interact with a first additive thatmodulates the first initiating energy light into UV light suitable foractivating the photo-initiator catalyzing the cure of the polymericadhesive and by adding a special additive (preferably an energymodulation agent, and preferably in powder form). The additive can beadded by weight or mole percent in the range of 1% to 30%. The adhesiveis then cured using the recommended curing using the first initiatingenergy. The 2 parts assembly (or subassembly) that has been joined usingthe adhesive goes through its functional life. After the functional lifeis over and the part is needed to be recycled then the assembly orsubassembly is exposed to a second initiating energy where the specialadditive absorbs the second initiating energy and emits UV energysuitable for breaking bonds of the curable adhesive to make thedis-assembling process easier and on demand. FIG. 3 shows a graphicaldepiction of this type of assembly wherein Parts A (10) and B (20) arejoined using an adhesive containing additives that modulate a deeplypenetrating energy to cure the adhesive and that further comprisesspecial additives able to modulate deeply penetrating radiation for thestructural disintegration of the adhesive (33).

Group 4: (Interlayering a Special Adhesive Between Two StandardAdhesives)

Two Commercially available polymeric adhesives (of various kinds)including 2 part adhesives, UV curable adhesives and thermally curableadhesives can be used in accordance to the current invention. A thirdadhesive (an adhesive containing the special additive (preferably anenergy modulation agent and preferably in powder form)) is added in thejoint between the assemblies and subassemblies to be bonded. Theadditive can be added by weight or mole percent in the range of 1% to30%. The Commercially available adhesives are then co-cured with thespecialty adhesive using the recommended curing method. The 2 partsassembly (or subassemblies) that have been joined using the commerciallyavailable adhesive goes through its functional life. After thefunctional life is over and the part is needed to be recycled then theassembly or subassembly is exposed to X-Ray where the special additiveabsorbs X-Ray energy and emits UV energy suitable for breaking bonds ofthe curable adhesive to make dis-assembling process easier and ondemand. FIG. 4 shows a graphical depiction of this type of assemblywherein Parts A (10) and B (20) are joined using an adhesive containingadditives that modulate a deeply penetrating energy for the structuraldisintegration of the adhesive (34), having a layer of commerciallyavailable adhesive (41 and 42) between the adhesive (34) and each ofParts A (10) and B (20). In the context of the above Groups 1-4, Parts A(10) and B (20) may be the same or different, and commercially availableadhesives (41 and 42) of Group 4 may be the same or different.

Application Examples

The four groups of adhesives described can be used for wide range ofapplications such as the bonding parts and de-bonding of partsincluding:

deformable substrates attached to other deformable substrates includingrubber to rubber;

deformable substrates attached to solid substrates such as rubber tometal, a semiconductor IC to a flexible substrate;

solid substrates to solid substrates such as silicon to FR4 or compositesubstrates to other composite substrate.

Primers:

Another aspect of the present invention extends to special primerswhereby the special primers that adhere to both the adhesive and theparts to be bonded is special in that it can be processed using standardprocess steps with the ability to become undone (to undergodeconstructive reactions) after being exposed to X-Ray. At least onepart needs to be primed in this case (preferably both). In these casesboth parts are free any contamination and the recycling yield out of thebonded parts is maximized. FIG. 5 shows one embodiment of this aspect ofthe invention wherein Part A′ (11) has a primed surface primed with aspecial primer (50), which is joined with Part B (20) using acommercially available adhesive (40). FIG. 6 shows another embodiment ofthis aspect of the invention wherein Part A′ (11) and Part B′ (21) areboth primed with special primers (51) and (52) (which may be the same ordifferent), and joined together on the primed surfaces using acommercially available adhesive (40).

Acid Digestion:

Another aspect of the present invention includes the use of assistedchemical digestion while the article is being exposed to the appliedenergy, such as X-Ray or E-Beam. Preferably, the chemical digestionoccurs in a chemical digestion bath containing a medium and a reactivecompound, wherein the reactive compound interacts with the intermediatelayer between the objects to be de-bonded, in order to accelerate thede-bonding process. Suitable reactive compounds include, but are notlimited to, various acidic and basic compounds reactive with theintermediate layer. Preferred reactive compounds include, but are notlimited to, mineral acids such as hydrochloric acid, sulfuric acid, andphosphoric acid; organic acids such as formic acid and acetic acid;alkali and alkaline metal bases, such as alkali metal or alkaline metalhydroxides, carbonates, etc. FIG. 7 is a graphical representation of anembodiment of the present invention in which an embodiment according toFIG. 5 is placed in an acid wash bath (60) during X-ray irradiation inorder to speed up the depolymerization.

Heat:

Heat can be added to speed up the kinetics of the various chemicalreactions involved in the present invention. For example, if desired,the de-bonding process can be accelerated by the application of heat tothe article being treated. The heating can be done at any desiredtemperature, and is preferably at a temperature of from room temperatureto 200° C., depending on the medium. Further, the heating can beperformed on the article being de-bonded during application of theapplied energy, or the article can be both immersed in a chemicaldigestion bath (such as the above noted acid wash for example), whilesimultaneously heating and applying the applied energy to causede-bonding. The effects of the chemical digestion bath and the heatingcan thus be maximized to cause accelerated de-bonding of the objectsforming the article.

Fiber Reinforced Composites:

Fiber reinforced Composites of different kinds can be formed by alamination process under heat and pressure. The constituents within agiven ply (or layer or lamina) of the composites include fibers, matrix,coupling agents or coatings, fillers.

The matrix can be thermosetting or thermoplastic matrix. Thethermosetting matrix can include (by way of illustration) diglycidylether of bisphenol A (DGEBA) epoxy resin and diethylene triamine (DETA)curing agent with fiber including carbon fibers or glass fibers.

Various thermoplastic resins can be used in the present inventionincluding PEEK (Cictrex (ICI), PPS (Ryton (Philips Petroleum)), PSUL(Udel (Amoco)), PEI (Ultem (GE)), PAI (Torlon(Amoco)), PAI (Amoco),K-III (Avimid (Dupont)), LARC-TPI (Durimid (Rogers)). Variousthermosetting resins can be used in the present invention includingBismaleimide (compimide 353 (Shell Chemical Co)), PMR-15, ACTP (Thermid600 (National Starch and Chemical Corp)).

The superposition of multiple plies can be done in various forms asshown in FIGS. 8A-8E, including FIG. 8A: unidirectional continuous, FIG.8B: bidirectional continuous, FIG. 8C: unidirectional discontinuous, andFIG. 8D: random discontinuous, followed by FIG. 8E: the lamination ofthe various plies, optionally with the application of pressure and heat.FIG. 9 shows a multi-ply construction using special primer layers (51,52, and 53) between each two adjacent plies, which permits recovery ofthe separate ply layers by use of the present invention, which is notobtainable by conventional recycling methods.

Rubber Tires:

Recycling of rubber is very challenging. It requires considerable energyinput to recover black carbon and steel out of the tire that the processis does not meet economic viability. Most rubbers are undergo SulfurCross Linking to improve cross link density. Vulcanization is an exampleof cross-linking. Schematic presentation of two “polymer chains” (blueand green) cross-linked after the vulcanization of natural rubber withsulfur (n=0, 1, 2, 3 . . . ).

The Phosphors can be use to break bonds in the rubber chains by virtueof their highly energetic energy. Phosphors can emit UVA, UVB and UVC topromote degradation of weak bond in the network. This embodiment isdepicted in FIG. 10.

Phosphors can be excited under X-Ray using KV beams and MV beams. The MVbeams will be powerful and cause more secondary electron cascade in thephosphors leading to more charged surfaces and to more creation ofradical oxygen species.

Pressure Sensitive Adhesives:

UV curable pressure sensitive adhesives—UV curable pressure sensitiveliquid and/or hot melt adhesives have been used for label, tape andself-adhesive insulation materials for several years. Although there isonly a limited range of cross linkable raw materials available,formulation of these materials has opened a wide range of new adhesives.Traditionally, hot melt pressure sensitive adhesives are formulated witha polyurethane resin with low molecular weight, acrylate functionaltackifying resins. Typical tackifying resins remain low molecular weightand thus have the desired properties to make the adhesive PSA. Theacrylate moiety can participate in UV induced crosslinking of the shortchain oligomer which results in the loss of its PSA characteristics andallows the material to be removed.

Many formulation factors can influence the performance of UV-curingpressure-sensitive adhesives (PSAs). Several basic material fundamentalsshould be considered, including polymer rheology, molecular weight,functionality and crosslink density. Most commercially availableUV-curing PSA systems are based on free-radical curing liquid systems,therefore emphasis will be on this technology.

Materials Fundamentals (how to Build a Polymeric System):

An understanding of the general fundamental material properties requiredof PSAs and, specifically, UV-curing PSAs will provide the formulatorwith the tools required to minimize trial-and-error approaches and speeddevelopment time. The most important fundamental materials propertiesfor PSA applications are:

-   -   Rheology    -   Molecular weight    -   Functionality

Rheology is the study of the change in form and flow of a matter. It isgenerally applied to viscoelastic materials. The rheological propertiesof the uncured adhesive are important with regard to application andcoating. However, they are also important in the cured state, as theymust be capable of a degree of flow to provide wetting and tack, yethave sufficient resistance to stress to provide for high adhesivestrength. The correct rheological properties for a PSA require a carefulbalancing of these properties. To counteract the viscous flow, PSAs arebased on very high-molecular-weight rubber polymers. These polymers relyon the entanglement of molecules to restrict flow. When high strength,heat resistance and chemical resistance are required, the entanglementsthemselves are not sufficient to restrict flow due to service stress. Inthese cases, the molecules are chemically crosslinked to provide for athree-dimensional network structure. This is the function of UV-curingmechanisms. In PSAs, the crosslink density or the molecular weightbetween crosslinks provides a measure of the balance that can beachieved between holding power and viscous flow. This crosslink densitycan also be measured by the glass-transition temperature of theadhesive. The higher the glass-transition temperature (Tg) for aspecific adhesive, the higher the crosslink density or the lower themolecular weight between crosslinks. Functionality plays an importantrole in determining crosslink density. The functionality of a polymer isthe number of reactive sites contained in the polymer molecule. Thereactive sites are the connecting points for crosslinking to take place.Therefore, the higher the functionality, the higher the crosslinkdensity, holding other factors constant. The discussion above considersthe base polymer in the UV-curing PSA formulation. In order to furthermodify the system to provide for the breadth of properties required fora practical adhesive, many additives and modifiers are also required.Thus, the adhesive formulator has many tools at his disposal. In fact,there are more tools than in conventional PSA formulation, due primarilyto the effect of UV dosage and possible oxygen inhibition on crosslinkdensity.

The conventional liquid UV-curable PSA is comprised of four essentialcomponents: oligomers, monomers, photoinitiator and additives. The widechoice of raw materials available allows maximum latitude to achieve thedesired properties. With conventional adhesives, the final performanceproperties are achieved during the resin polymerization process in areactor. With UV technology, the polymerization takes place during thecuring process. In effect, radiation-curable adhesives are aself-contained polymer factory of sorts.

Oligomers determine the overall properties of any adhesive crosslinkedby radiant energy. Oligomers are moderately low-molecular-weightpolymers, most of which are based on the acrylation of differentstructures. The acrylation imparts the unsaturation or C═C group to theends of the oligomer; this serves as the functionality. The oligomerused in PSA applications is generally a multi-functional elastomericpolymer, such as an aliphatic urethane acrylates. Oligomers provide muchof the shear strength in the UV PSA formulation. However, selection ofthe oligomer will also affect more viscous properties, such as tack andpeel strength. The high-molecular-weights and glass-transitiontemperatures are generally well below room temperature to allow theoligomer to offer elastic properties at room temperature. This providesthe viscoelasticity required for good tack and adhesion. Other factorsthat are affected by choice of oligomer include: reactivity, creepresistance, heat and chemical resistance, and color retention. Ofcourse, cost is also an important factor as oligomers often have thegreatest weight concentration in an adhesive formulation.

In the acrylate family, there are several possible UV-curing oligomersthat can be used in PSA formulations. Each of these has certainadvantages and disadvantages. Epoxy acrylates are one of the dominantoligomers in the radiation-curable coatings market. In most cases, epoxyacrylates do not have any free epoxy groups left from their synthesisbut react through their unsaturation.

Urethane acrylates are produced by reacting polyisocyanates withhydroxyl alky acrylates, usually along with hydroxyl compounds, toproduce the desired set of properties. Urethane acrylates are the mostexpensive of the acrylates. There are many different types of urethaneacrylate oligomers that feature variations in the following parameters.

A variety of polyester acrylates is available, which enables a range ofproperties. They are generally low-viscosity resins that require noreactive diluents. Polyester acrylates provide performance propertiesbetween those of urethane acrylates and epoxy acrylates. A disadvantageof some types of polyester acrylate is their irritancy. This isparticularly true for low-molecular-weight, highly reactive resins.

Polyester acrylates vary in functionality, chemical backbone andmolecular weight. The influence of the functionality is similar to thatfor the urethane acrylates. The chemical backbone has a large influenceon properties such as reactivity, color stability, hardness, reactivity,etc. Typically, the higher the molecular weight, the higher theflexibility and viscosity and the lower the reactivity.

Polyether acrylates have the lowest viscosity of the acrylate resins andare typically used with very little monomer or reactive diluents. Theygenerally have high flexibility but relatively poor water and chemicalresistance. To overcome these drawbacks, polyether acrylates are mostlyused in combinations with other oligomers or monomers. An interestingproperty of some polyether acrylates is that they are compatible withwater and can be used in water dilutable systems.

Acrylic acrylates, like urethane acrylates, have a very versatilechemistry, and there are many variations available to the formulator.These resins are often used because of their good adhesion to difficultsubstrates, such as low-surface-energy plastics.

Miscellaneous oligomers are generally specialty products that typicallycomprise melamine acrylates, silicone acrylates, etc. Other types ofradiation-curable resins include unsaturated polyesters dissolved instyrene or acrylics. More recently, polyester resins have appeared onthe market in the form of non-acrylic vinyl ether blends.

Monomers are primarily used to lower the viscosity of the uncuredmaterial and to facilitate application. However, they are also used tomake adjustments of the formulation, such as improved surface wetting,leveling, and physical properties. Since most oligomers are too viscousto be applied with conventional coating equipment, most radiation-curedformulations are diluted down to a viscosity of 100-10,000 cps by addinga lower-molecular-weight monomer.

There are primarily two types of monomers: monofunctional, which areused primarily as a diluent; and multifunctional, which can be used as adiluent and crosslinker. Multifunctional monomers can be di-, tri-, andpolyfunctional. The greater the functionality, the greater thecrosslinking potential of the monomer. In this way, the functionalmonomers can be used to adjust properties of the final adhesive as wellas to reduce viscosity.

Monomer chemistry also has an influence on the polymerization processand physical properties of the final adhesive. Increasing the monomerfunctionality leads to higher cure speed, higher Tg, higher crosslinkdensity, higher shear strength, and greater chemical and thermalresistance, but lower flexibility and low conversion. A balance isgenerally required between adhesive strength and rigidity. Rigidadhesives have high shear strength and chemical/thermal resistance butexhibit low peel strength. More flexible adhesives have high peel andimpact strength and better adhesion to plastic substrates, but they donot have the heat and chemical resistance of their more denselycrosslinked (more rigid) counterparts.

The monomer used as a reactive diluent in a UV-curable resin plays a keyrole: it affects both the cure speed and the polymerization extent, aswell as the properties of the final product. An increase in monomerfunctionality generally accelerates the curing process, but at theexpense of the overall monomer conversion. Poor conversion leads to acrosslinked polymer, which contains a substantial amount of residualunsaturation. As a result of increased crosslink density, UV adhesivesbecome more rigid and more resistant to chemicals, temperatures, andabrasion. However, they become less flexible and less resistant toimpact and thermal cycling.

The effect of monomer on glass-transition temperature (which is a resultof crosslink density) is an important tool for the formulator since themechanical properties of the adhesives are strongly influenced by theTg. If the Tg of the adhesive is below the expected service temperature,the adhesive will generally exhibit some of the following properties.

-   -   Flexible with a high degree of elongation    -   High peel and impact strength    -   Good resistance to thermal cycling    -   High thermal expansion coefficient (well suited for plastic        substrates)    -   High degree of creep when exposed to constant stress    -   Poor blocking resistance (tacky)    -   High moisture uptake    -   Good chemical and temperature resistance

On the other hand, if the Tg is above the expected service temperature,then the adhesive usually can be characterized as exhibiting some of thefollowing qualities:

-   -   Rigid and to some extent brittle    -   Low impact and peel strength    -   Prone to crack propagation    -   Low thermal expansion coefficient    -   Poor resistance to thermal cycling    -   High shear strength    -   Low water uptake and swelling, and high barrier properties        against chemicals and water    -   High temperature and chemical resistance.

The range of radiation-curable reactive monomers offered today is almostunmanageable. Formulators who have to provide optimum productperformance at the best cost are sometimes overwhelmed by the vast arrayof choices. Because there are so many monomers available, it isimportant to keep in mind some general guidelines. There are four majorparameters that contribute to the monomer's characteristics:functionality, chemical backbone, chemical structure and molecularweight.

The type and molecular weight of the backbone chain in a monomer can bevaried to provide lower skin irritation, better flexibility, and fastercure speeds. Monomers can also be tailored for water-dispersible,adhesion-promoting and pigment-dispensing applications. In addition toproviding the functions noted above, monomers could be used as achemical intermediate to produce copolymers that enhance performanceproperties.

Photoinitiators

Photoinitiators absorb light and are responsible for the production offree radicals. High-energy free radicals induce crosslinking between theunsaturation sites of monomer, oligomers and polymers. Arguably, themost important additive is a photoinitiator for UV-cured adhesives.Photoinitiators are not needed for electronic beam-cured systems becausethe electrons themselves are able to initiate crosslinking by virtue oftheir higher energy. A typical photoinitiator for a UV-curable acrylicsystem is based on an aromatic keto compound. Often more than onephotoinitiator is employed to provide for cure with a specific radiationsource. The photoinitiator package will also need to be optimized for agiven adhesive thickness and UV dosage.

The photoinitiator determines not only how but where the cure willoccur. A high-surface-cure photoinitiator, for example, tends toincrease shear properties while destroying the tack of the system. Agood through-cure product may leave the surface very tacky but exhibitpoor cohesive strength due to the fact that the surfaces are not wellcrosslinked.

Conventionally, UV curing requires that the adhesive has to betransparent to UV light in order to be cured. Filled or pigmentedadhesives may pose a curing challenge.

Another disadvantage is that one transparent substrate is normallyrequired, and a limited depth of cure can be achieved. Thesedisadvantages have generally been overcome by the development ofdual-cure adhesive systems. In these systems, two independent curingmechanisms are incorporated into a single formulation. The adhesives canbe cured first to a chemically stable state by UV radiation and thenadvanced to a full cure by a second means such as thermal cure.

Other Additives

The most common additives in all UV-cured resins are stabilizers, whichprevent gelation in storage and premature curing due to low levels oflight exposure. Color pigments, dyes, defoamers, adhesion promoters,flatting agents, wetting agents and slip aids are examples of otheradditives. Tackifiers are required in pressure-sensitive radiant-curedadhesives to improve the tack and pressure-sensitive nature or“stickiness” of the adhesive. Traditionally, these formulations haveincluded tackifiers consisting of solid rosin esters of C-5 and C-9hydrocarbon resins.

However, solid tackifying agents are difficult to incorporate intoUV-curable oligomers and monomers without the use of a solvent and/orheat. This is often a time-consuming and expensive process. Newlow-viscosity oligomers have been developed that are said to provideexcellent tack properties without the need of a solid resin additive.

The adhesive materials are typically dispensed as a thixotropic fluid inprecise locations, and after all the parts are placed, the entireassembly is heated to a temperature necessary to polymerize the monomersor crosslink resins. The adhesion of two objects is done by adding theadhesive material at the interface of two objects to be bonded. Thepotential elimination of the addition of a third layer (the adhesive inthis case) would be of great benefits. The tool used to dispense anadhesive is eliminated and the step required to cure the adhesive underheat is also obsoleted which saves overall cycle time.

As modern assembly methods evolve and more process steps are streamlined for a more efficient and more vertically integrated process stepsto maximize assembly tool utilization, the permissible thermal budgetand process cycle time during assembly continues to decrease. Fastermanufacturing and higher yields are always of great benefits to themanufacturers.

The clear limitation of conventional photo-initiators is the need tohave direct line-of-sight access to a suitable light source. The clearlimitation of conventional thermally activated adhesive is the inherentpoor thermal conductivity of the materials to be bonded which results ina long process time. The direct welding of two interfaces would behighly desirable.

Furthermore, the assemblies used for various commercial products arerelatively small. While electron beam can deliver a desirable source ofradiation, the electron beam is not compact and is more applicable tolarge form factors (such is the case of a wide web process for example).X-Ray energy is delivered through a more compact set of equipment andcan integrated in various tools for more efficient tool utilization. Inthe present invention a bonding method that is vertically integrated isdiscussed.

Special Additives of the Present Invention: Light Modulating Particles,which May Contain Coatings:

The light modulating particles refers to any material that can absorbX-Ray and emit another wavelength preferably in the UV (which is aphoto-catalytic light). By way of examples the light mediating particlescan include (Phosphors, Quantum Dots and Scintillators, diamonds withadequate defect centers and densities). All these particles will bereferred to as phosphors interchangeably and therefore examples given byway of preparations are applicable to QDs, diamonds and scintillators.

The various light modulating media (phosphor) particles were coatedusing PMMA. FIG. 11A is a graphical representation of an uncoatedphosphor and a coated phosphor. The process was performed by firstdissolving PMMA into Acetone and then rolling the phosphors with thesolution in a ball mill using 5 mm zirconia as the grinding and mixingballs. The solution is then recovered and then dried. Upon acetoneevaporation the particles were left with a surface coating of PMMA, asshown in FIG. 11B. If phosphors of different types are subjected tocoating in a ball mill simultaneously, the result is a number of powdersof mixed kind that are individually coated when ball milling is used, asshown in FIG. 11C. The thickness of the coating can be estimated fromthe surface area of the particles and the concentration of PMMA or ofEthyl cellulose that is dissolved in a diluent.

Furthermore, the PMMA or Ethyl Cellulose coating can include some of thedesirable organic peroxide chemistries. These chemistries can be addedin liquid forms and can be rolled in a jar in the ball mill in acetone.Upon drying the solvent, the PMMA or Ethyl cellulose coating is dopedwith the organic peroxide chemistry, which is depicted in FIG. 11D. Asan example Dicumyl peroxide can be added at 1% by weight in the previoustable.

If the particles are not completely dispersed then an aggregate of thephosphors is coated with the PMMA resin, as depicted in FIG. 11E.

Furthermore, if phosphors of different kind are used then an aggregateof different phosphor can be coated using PMMA, as depicted in FIG. 12A,or coated and imparted with peroxide chemistry, as depicted in FIG. 12B.The Molecular Weight of the PMMA used can vary, and its selection iswithin the skill of one of ordinary skill in the art.

By adding the weight percent in the mix to high enough levels above 0.03g per 1 g of phosphors, the coating is no longer forms a discontinuousphase where individual particles are coated; but, rather, the particlesstart to neck and to connect laterally which culminates in the formationof a film. At a ratio of 5 weight percent of higher, the necking ofparticles enables the formation of a film. The film is obtained bytaking the slurry and using a drawing knife. The conformable film can bedrawn using a 1 mill to 8 mill knife, as shown in FIG. 13A, providing aphosphor coated conformable film depicted in an overhead view in FIG.13B. A die cutter can be used to obtain various geometries cut from thephosphor loaded conformable film as shown in FIG. 13C. The resultingconformable film, or its die-cut shapes, can accommodate stretching andmaintaining its shape across complex interfaces, as shown in FIG. 13D.

Furthermore, the preparation of the film can be done using plasticizersin the mix prior to casting. About 2% to 5% by weight is a desirablerange. Plasticizers with boiling points temperatures above roomtemperature remain embedded in the film and make the film's surfacesticky. This is desirable in case the film is to be used between twoobjects to be adhered. Examples of suitable plasticizers includeTripropylene glycol. The addition of a small amount of Tripropyleneglycol in the film (around 2% by weight of solids) and the placement ofthe film at the interface of two objects allows a good materialtransport between the objects and promotes bonding. ExcessiveTripropylene glycol would prohibit adhesion.

H[OC₂H₃(CH₃)]₃OH

Tripropylene Glycol MV Vs KV Beams

A further embodiment of the present invention provides a method forde-bonding objects contained in an article at an interface between theobjects, wherein the objects are joined at the interface through anintermediate layer, comprising applying energy from a radiation source,wherein the energy is sufficient to cause destruction of bonds withinthe intermediate layer; and separating the two objects from one another.In this particular embodiment, the intermediate layer is an adhesivelayer used to join the objects together, wherein the adhesive layer isformed from a curable adhesive composition comprising one or morecurable monomers and one or more energy modulation agents. The adhesivelayer is formed by applying an applied energy to the curable adhesivecomposition, wherein the one or more energy modulation agents convertthe applied energy into an initiation energy which initiatespolymerization of the one or more monomers and thus causes curing of thecurable adhesive composition. In a preferred embodiment, the appliedenergy is a first ionizing radiation, more preferably selected from thegroup consisting of x-rays, gamma rays, and electron beams, mostpreferably x-rays. In a further preferred embodiment, the x-rays used asthe applied energy for curing the curable adhesive layer have an energyof from 1 kV to 250 kV.

In the debonding portion of this embodiment, the one or more energymodulation agents are used to convert an externally applied energy intoan energy sufficient to cause destruction of bonds within the previouslyformed adhesive layer. In a preferred embodiment, the externally appliedenergy is a second ionizing radiation, more preferably selected from thegroup consisting of x-rays, gamma rays, and electron beams, mostpreferably x-rays. In a further preferred embodiment, the secondionizing radiation used in the debonding portion of the embodiment hasan energy of 1 MV or higher, more preferably x-rays having an energy of1 MV or higher.

Alternatively, rather than using low energy (on the order of kV's) tocure and high energy (on the order of MV's) to depolymerize, it is alsopossible to use a low dose and/or lower dose rate of energy to cure,with a higher dose and/or higher dose rate to cause depolymerization.

Initiation Energies KV Vs MV Vs E-Beam

Listed below are the approximate wavelength, frequency, and energylimits of the various regions of the electromagnetic spectrum.

Wavelength (m) Frequency (Hz) Energy (J) Radio >1 × 10⁻¹  <3 × 10⁹  <2 ×10⁻²⁴ Microwave 1 × 10⁻³-1 × 10⁻¹  3 × 10⁹-3 × 10¹¹ 2 × 10⁻²⁴-2 × 10⁻²²Infrared 7 × 10⁻⁷-1 × 10⁻³ 3 × 10¹¹-4 × 10¹⁴ 2 × 10⁻²²-3 × 10⁻¹⁹ Optical4 × 10⁻⁷-7 × 10⁻⁷  4 × 10¹⁴-7.5 × 10¹⁴ 3 × 10⁻¹⁹-5 × 10⁻¹⁹ UV 1 × 10⁻⁸-4× 10⁻⁷ 7.5 × 10¹⁴-3 × 10¹⁶  5 × 10⁻¹⁹-2 × 10⁻¹⁷ X-ray 1 × 10⁻¹¹-1 ×10⁻⁸  3 × 10¹⁶-3 × 10¹⁹ 2 × 10⁻¹⁷-2 × 10⁻¹⁴ Gamma-ray <1 × 10⁻¹¹ >3 ×10¹⁹ >2 × 10⁻¹⁴

As shown in FIG. 14, initiation energy in the form of radiation from theinitiation energy source permeated throughout the medium. The initiationenergy source can be an external energy source or an energy sourcelocated at least partially in the medium. Activatable agents and/or theenergy modulation agents can include plasmonics agents which enhanceeither the applied energy or the energy emitted from the energymodulation agents so as to directly or indirectly produce a change inthe medium.

In various embodiments, the initiation energy source may be a linearaccelerator equipped with at least kV image guided computer-controlcapability to deliver a precisely calibrated beam of radiation to apre-selected coordinate. One example of such linear accelerators is theSMARTBEAM™ IMRT (intensity modulated radiation therapy) system (fromVarian Medical Systems, Inc., Palo Alto, Calif.) or Varian OBItechnology (OBI stands for “On-board Imaging”, and is found on manycommercial models of Varian machines). In other embodiments, theinitiation energy source may be commercially available components ofX-ray machines or non-medical X-ray machines. X-ray machines thatproduce from 10 to 150 keV X-rays are readily available in themarketplace. For instance, the General Electric DEFINIUM series or theSiemens MULTIX series are two non-limiting examples of typical X-raymachines designed for the medical industry, while the EAGLE PACK seriesfrom Smith Detection is an example of a non-medical X-ray machine.Another suitable commercially available device is the SIEMENS DEFINITIONFLASH, (a CT system), by Siemens Medical Solutions. As such, theinvention is capable of performing its desired function when used inconjunction with commercial X-ray equipment.

According to another embodiment of the invention, energy modulationagents can be placed in the vicinity of a fluid medium (e.g., a liquidor other fluid-like medium) and held inside a container. The containercan be made of a material that is “transparent” to the radiation. Forexample, plastic, quartz, glass, or aluminum containers would besufficiently transparent to X-rays, while plastic or quartz or glasscontainers would be transparent to microwave or radio frequency light.The energy modulation agents can be dispersed uniformly throughout themedium or may be segregated in distinct parts of the medium or furtherseparated physically from the medium by encapsulation structures. Asupply would provide the medium to the container.

FIG. 15 is a schematic depicting x-ray scattering events andinteractions with energy modulation agents in the medium. In oneembodiment, the effect produced by the interactions of the x-rays andenergy modulation agents with the medium occurs by pathways not yetcertain where internally produced light (IR, visible, and/or UV) aloneor in combination with the x-ray exposure drive a chemical reaction inthe medium or to the energy modulation agents themselves. These pathwaysmay be influenced by the generation of free radicals inside the medium.These pathways may alternatively, or in addition, be influenced by thegeneration of ionized species inside the medium. These pathways includethe disassociation of salts that in turn create a desirable chemicalreaction. These pathways may be influenced by the scattering of x-raysinside the medium. These pathways may be influenced by the generation ofemitted and re-emitted light inside the medium. These pathways may be acombination of these factors.

Further, these pathways may include the in situ generation of singletoxygen and/or ozone to produce a change in the medium. For example, thephotoactivatable agents may be stimulated through mechanisms such asirradiation, resonance energy transfer, exciton migration, ion-exchange,free radicals, electron injection, or chemical reaction to where“activated” agent is capable of producing the predetermined changedesired.

In another embodiment, clusters of energy modulations agents (orchemically reactive agents or plasmonic agents) may be provided to alocal site where x-ray exposure or internally generated light breaksapart the clusters into a form more useful to treatment at the localsite or more useful to generating a local change in the medium nearbywhere the clusters existed.

Coatings on Phosphors that can Yield Easier Degradation

Some phosphor coating can participate in the initial curing and breakthe crosslinks by virtue of breaking the coating. For example, the useof a coating susceptible to cleavage by an applied radiation can lead tocompositions that can be cured by one wavelength of applied radiation(which does not affect the coating), and de-bonded or deconstructed byapplication of a different radiation causing the phosphor coating tobreak, and thus creating weaknesses in the previously cured material.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A method for de-bonding objects contained in an article at aninterface between the objects, wherein the objects are joined at theinterface through an intermediate layer, comprising: providing thearticle comprising the objects bonded at the interface through theintermediate layer, wherein the intermediate layer comprises an adhesivelayer formed by curing a curable adhesive composition by application ofa first x-ray source having a first x-ray energy, wherein the curableadhesive composition comprises one or more curable monomers and one ormore energy modulation agents, whereby the one or more energy modulationagents convert the first x-ray energy into an initiation energy whichinitiates polymerization of the one or more monomers and thus causecuring of the curable adhesive composition; applying to the article asecond x-ray energy from a second x-ray source, wherein the second x-rayenergy is different from the first x-ray energy, and wherein the secondx-ray energy is converted by the one or more energy modulation agentsinto an energy that is sufficient to cause destruction of bonds withinthe intermediate layer; and separating the objects from one another. 2.The method of claim 1, wherein the first x-ray energy is lower energythan the second x-ray energy.
 3. The method of claim 1, wherein thefirst x-ray energy is higher energy than the second x-ray energy.
 4. Themethod of claim 2, wherein the first x-ray energy is from 1 kV to 250kV, and the second x-ray energy is 1 MV or higher.
 5. The method ofclaim 1, wherein the first x-ray energy has an energy of from 1 kV to200 kV.
 6. The method of claim 2, wherein the first x-ray energy has anenergy of from 1 kV to 200 kV.
 7. The method of claim 4, wherein thefirst x-ray energy has an energy of from 1 kV to 200 kV.
 8. The methodof claim 1, wherein the one or more energy modulation agents convert thesecond x-ray energy into UV energy sufficient to cause destruction ofbonds within the intermediate layer.
 9. The method of claim 1, whereinthe second x-ray energy has an energy of 1 MV or higher.
 10. The methodof claim 1, wherein the applying the second x-ray energy is performedwhile the article is immersed in a chemical digestion bath comprising amedium and an acid compound.
 11. The method of claim 1, wherein theapplying the second x-ray energy is performed while the article isheated to a temperature of from room temperature to 200° C.
 12. Themethod of claim 10, wherein the immersed article is also heated to atemperature of from room temperature to 200° C.
 13. A method forpreparing an article by bonding objects at an interface between theobjects, wherein the objects are joined at the interface through anintermediate layer, comprising: providing an assembly of the objectshaving the intermediate layer at the interface thereof, wherein theintermediate layer comprises an adhesive layer comprising a curableadhesive composition, wherein the curable adhesive composition comprisesone or more curable monomers and one or more energy modulation agents;applying a first x-ray source having a first x-ray energy, whereby theone or more energy modulation agents convert the first x-ray energy intoan initiation energy which initiates polymerization of the one or moremonomers and thus causes curing of the curable adhesive composition,thus bonding the objects together; wherein the one or more energymodulation agents contained in the intermediate layer of the bondedarticle can be used to separate the objects from one another by applyingto the article a second x-ray energy from a second x-ray source, whereinthe second x-ray energy is different from the first x-ray energy, andwherein the second x-ray energy is converted by the one or more energymodulation agents into an energy that is sufficient to cause destructionof bonds within the intermediate layer.
 14. The method of claim 13,wherein the first x-ray energy is lower energy than the second x-rayenergy.
 15. The method of claim 13, wherein the first x-ray energy ishigher energy than the second x-ray energy.
 16. The method of claim 14,wherein the first x-ray energy is from 1 kV to 250 kV, and the secondx-ray energy is 1 MV or higher.
 17. The method of claim 13, wherein thefirst x-ray energy has an energy of from 1 kV to 200 kV.
 18. The methodof claim 13, wherein the first x-ray energy has an energy of from 1 kVto 200 kV.
 19. The method of claim 16, wherein the first x-ray energyhas an energy of from 1 kV to 200 kV.
 20. The method of claim 13,wherein the one or more energy modulation agents can convert the secondx-ray energy into UV energy sufficient to cause destruction of bondswithin the intermediate layer.
 21. The method of claim 13, wherein thesecond x-ray energy has an energy of 1 MV or higher.
 22. The method ofclaim 13, wherein the ease of debonding of the article can be increasedby applying the second x-ray energy while the article is immersed in achemical digestion bath comprising a medium and an acid compound. 23.The method of claim 13, wherein the ease of debonding of the article canbe increased by applying the second x-ray energy while the article isheated to a temperature of from room temperature to 200° C.
 24. Themethod of claim 22, wherein the ease of debonding of the article can befurther increased by heating the immersed article to a temperature offrom room temperature to 200° C.